MB-100: handle Errno 32: Broken pipe in _get_connection

http://qa.hq.northscale.net/view/2.0.1/job/centos-64-2.0-upgrade/82/consoleFull

Change-Id: I5d112e4fe304e1de642e41ce009fdc0fb24d8f26
Reviewed-on: http://review.couchbase.org/24655
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>